Not Applicable.
1. Technical Field
This invention relates to a large projection display apparatus, used for example, to display video images, and more particularly to a tiled display system with multiple projectors using fiber optics and a co to route illumination from one or more remote light sources to these projectors.
2. Background Art
There is an anticipated demand among consumers for high-definition large screen displays for such applications as home theater and advertising. Typical liquid crystal displays (LCD) for consumer applications have SVGA resolution of approximately 600xc3x97800 pixels, although high-end projection displays have been introduced with up to 1920xc3x971080. Displaying such low resolution on a large display yields unacceptable picture quality; for instance an SVGA display projected as a 10-foot diagonal image has a minimum pixel size of approximately xe2x85x9-inch by xe2x85x9-inch. Furthermore, high-definition television HDTV has a width to height aspect ratio of 16:9 as opposed to computer monitors and standard television, which have a width to height aspect ratio of 4:3.
There have been several attempts in the past to make a large size projection display, based on combining several smaller projected image xe2x80x98tilesxe2x80x99 into a larger composite tiled image, such as in Bleha, et al (U.S. Pat. No. 6,017,123). These prior art systems have generally proved less than satisfactory, because of a lack of both brightness and color uniformity between the tiles. This lack of uniformity is typically caused by the use of multiple projection lamps where each lamp exhibits differing brightness and color characteristics as compared to the other lamps in the system. Even if matching light sources, typically metal halide lamps, are chosen, the brightness and color characteristics will change as the lamps age.
In an attempt to compensate for this lack of brightness and color uniformity, the prior art teaches a camera connected to an image processing function that individually modifies each projected image such as described in Johnson et al, (U.S. Pat. No. 6,219,099). Disadvantageously, the Johnson image processing function sacrifices a number of gray shades available for the displayed image in order to compensate for the lack of brightness and color uniformity between the projected tiles.
Another problem with prior art projection displays is that a high-intensity light source, such as a metal halide lamp, is required and this high-intensity light source typically produces a large amount of heat that can reduce the reliability of projection image display elements such as liquid crystal displays.
FIG. 1 shows an example of a conventional projection type display apparatus as discussed in Kodama, et al. (U.S. Pat. No. 6,212,013), which would be used for a single display or for each display tile of a tiled display.
Referring to FIG. 1, white light emitted from a light source unit 1 having a reflector 2 travels through lenses 3 and 4, converter 5, and lens 6, impinging upon a dichroic mirror DM1 which transmits a red light component R but reflects a green light component and a blue light component. Then the red light component transmitted by the dichroic mirror DM1 is reflected by a total reflection mirror M1 through a field lens 7R and a trimming filter TR into a red image display element 8R, in which the red light component is optically modulated according to an input signal. The red light component light thus optically modulated is combined with a modulated blue light component and a modulated green light component within a dichroic prism 9 and transmitted into a projection lens 10.
On the other hand, among the blue and green light components reflected by the dichroic mirror DM1, the green light component G is reflected by another dichroic mirror DM2 through a field lens 7G and a trimming filter TG into a green image display element 8G, in which the green light component is optically modulated according to an input signal. The green light component light thus optically modulated is combined with the modulated red light component and a modulated blue light component within the dichroic prism 9 and transmitted into the projection lens 10. Further, the blue light component B transmitted by the dichroic mirror DM2 travels via a condenser lens 11, a total reflection mirror M2, a relay lens 12, a total reflection mirror M3, and a field lens 7B into a blue image display element 8B, in which the blue light component is optically modulated according to an input signal. The blue light component thus optically modulated is combined with the modulated red light component and the modulated green light component within the dichroic prism 9 and transmitted into the projection lens 10. Then trichromatic light combined by the combining dichroic prism 9 is projected by the projection lens 10 toward a target screen or display tile, not shown.
There continues to be long felt need in the display industry for a high-definition large screen with uniform color and brightness characteristics and with a high-intensity light source for a tiled projection display.
My invention produces high-intensity white light from a common light source, separates this high-intensity white light into high-intensity primary color light components, and couples these high-intensity primary color light components to multiple projectors using fiber optic cables. Advantageously, my projection display system does not use a separate lamp for each display tile and thereby achieves uniform display brightness and color uniformity across the entire projected display area, for example 9 feet high by 16 feet wide. One novel aspect of my invention allows multiple light sources to be combined to provide lamp redundancy and yet act as a single light source with regard to both color and brightness uniformity.
One embodiment of my invention uses three imaging devices per display tile, such as transmissive polysilicon (Poly-Si) liquid crystal (LC) imaging devices, with each imaging device assigned to a primary color selected from the group of red, green, and blue.
Another embodiment of my invention uses a single imaging device to drive each display tile with all three primary colors in a frame sequential (FS) manner. In a particular embodiment, the frame sequence displays red information first, followed by green, and followed by blue in a perpetual cycle, at a rate fast enough to allow a human brain to integrate the images as if they were displayed simultaneously. Advantageously, this embodiment of my invention thus minimizes that total number of imaging devices required.